Carbon fibers have been used in a wide variety of applications because of their desirable properties such as high strength and stiffness, high chemical resistance, and low thermal expansion. For example, carbon fibers can be formed into a structural part that combines high strength and high stiffness, while having a weight that is significantly lighter than a metal component of equivalent properties. Increasingly, carbon fibers are being used as structural components in composite materials for aerospace applications. In particular, composite materials have been developed in which carbon fibers serve as a reinforcing material in a resin or ceramic matrix.
In order to meet the rigorous demands of the aerospace industry, it is desirable to continually develop new carbon fibers having both high tensile strength (1,000 ksi or greater) and high modulus of elasticity (50 Msi or greater), as well as having no surface flaws or internal defects. Carbon fibers having individually higher tensile strength and modulus can be used in fewer quantities than lower strength carbon fibers and still achieve the same total strength for a given carbon fiber-reinforced composite part. As a result, the composite part containing the carbon fibers weighs less. A decrease in the structural weight is important to the aerospace industry because it increases the fuel efficiency and/or increases the load carrying capacity of the aircraft incorporating such a composite part.